JPH0339969A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic sensitive body high in sensitivity and superior in repetition characteristics and dark decay characteristics by regulating the content of ionic impurities in a metal-free phthalocyanine as an electric charge generating material to <=250mug/g. CONSTITUTION:The electrophotographic sensitive body is formed by successively laminating on a conductive substrate 1 a charge generating organic layer 2 containing the charge generating material of the metal-free phthalocyanine having the content of the ionic impurities regulated to <=250mug/g, and a charge transfer layer 3 each by preparing a coating fluid and coating with it, thus permitting the obtained electrophotographic sensitive body to be superior in electrophotographic characteristics, such as sensitivity, dark decay characteristics, and repetition characteristics.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and more specifically, it is equipped with a charge generation layer and a charge transport layer made of an organic material, and is suitable for use in electrophotographic printers, copying machines, etc. The present invention relates to a laminated electrophotographic photoreceptor that is used.

[Conventional technology]

Conventionally, photosensitive materials for electrophotographic photoreceptors (hereinafter also referred to as photoreceptors) include inorganic photoconductive substances such as selenium or selenium alloys, or inorganic photoconductive substances such as zinc oxide or cadmium sulfide in a resin binder. dispersions, organic photoconductive materials such as poly-N-vinylcarbazole or polyvinylanthracene, phthalocyanine compounds or bisazo compounds, or dispersions of these organic photoconductive materials in resin binders. Dispersed ones are used.

In addition, a photoreceptor must have the function of retaining a surface charge in the dark, the function of receiving and receiving light to generate a charge, and the function of receiving light and transporting a charge. We developed a so-called single-layer photoreceptor that has both of these functions, and a layer that is functionally separated into a layer that mainly contributes to charge generation, a layer that contributes to surface charge retention in the dark, and a layer that contributes to charge transport during light reception. There is a so-called laminated type photoreceptor. For example, the Carlson method is applied to image formation by electrophotography using these photoreceptors. Image formation in this method involves charging the photoconductor in a dark place by corona discharge, forming electrostatic latent images such as letters and cypress on the original by exposing the surface of the charged photoconductor, and This is done by developing a latent image with toner, transferring the developed toner image to a support such as paper, and fixing it. After the toner image has been transferred, the photoreceptor is subjected to static neutralization, removal of residual toner, photostatic static elimination, etc. Subject to reuse.

In recent years, electrophotographic photoreceptors using organic materials have been put into practical use due to their advantages such as flexibility, thermal stability, and film-forming properties. For example, polyJ-N-vinylcarbasol and 2
．． A photoreceptor comprising 4.7-trinitrofluoren-9-one as described in U.S. Pat. No. 3,484,237,
Photoreceptor containing organic pigment as main component (Japanese Patent Application Laid-Open No. 47-3754
3), and a photoreceptor whose main component is a eutectic complex consisting of a dye and a resin (described in JP-A-47-10785).

[Problem to be solved by the invention]

As mentioned above, organic materials have many advantages that inorganic materials do not have, but at present, it is not yet possible to obtain a material that satisfies all the characteristics required of a photoreceptor, especially in terms of photosensitivity and Dark decay characteristics.

There were problems with the characteristics when used repeatedly and continuously.

An object of the present invention is to provide a photoreceptor that includes a charge generation layer and a charge transport layer made of an organic material and has excellent electrophotographic properties such as photosensitivity, dark decay properties, and repeatability properties.

[Means to solve the problem]

According to the present invention, the above-mentioned problem is solved because, in a photoreceptor comprising a charge generation layer and a charge transport layer made of an organic material on a conductive substrate, the charge generation substance of the charge generation layer is metal-free phthalonanine. , and the proportion of ionic impurities contained in this metal-free phthalocyanine is 250.
This problem can be solved by using a photoreceptor with a photoreceptor that has a photoconductivity of μs/g or less.

[Effect]

In order to solve the above-mentioned problems, the present inventors have carried out intensive evaluation studies on various charge-generating substances, and as a result of conducting numerous experiments, the present inventors have found that, although the technical clarification has not yet been fully elucidated, ion ions can be used as charge-generating substances. The proportion of sexual impurities is 250μ
They discovered that the use of metal-free phthalocyanine having a content of less than g/g is effective in improving electrophotographic properties, and they were able to obtain an excellent photoreceptor.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 are conceptual cross-sectional views showing different embodiments of the photoreceptor of the present invention, where l is a conductive substrate, 2 is a charge generation layer, 3 is a charge transport layer, and 4 is a coating layer. .

The conductive substrate 1 serves as an electrode for the photoreceptor and at the same time serves as a support for other layers, and may be cylindrical, plate-shaped, or film-shaped, and may be made of aluminum, stainless steel, or nickel. It may be made of gold rR1, glass, resin, or the like, which is subjected to conductive treatment.

The charge generation layer 2 is formed by vacuum-depositing an organic photoconductive substance or by coating a material in which particles of an organic photoconductive substance are dispersed in a resin binder, and is capable of receiving light. Generates electric charge. In addition to the high charge generation efficiency, the ability to inject the generated charges into the charge transport layer 3 is also important, and it is desirable that the charge is less dependent on the electric field and can be easily injected even in a low electric field.

Since the charge generation layer only needs to have a charge generation function, its thickness is determined by the light absorption coefficient of the charge generation substance and is generally 5.
It is 1 μm or less, preferably 1 μm or less. The charge generation layer is mainly composed of a charge generation substance, and a charge transport substance or the like may be added thereto.

The charge transport layer 3 is a coating film made of a material in which an organic charge transport substance is dispersed in a resin binder, and in the dark, it serves as an insulating layer to retain the charge on the photoreceptor, and when receiving light, it is injected from the charge generation layer. Demonstrates the function of transporting electric charge. Examples of organic charge transport substances include pyrazoline, hydrazone, and triphenylmethane.

Derivatives such as styryl and oxadiazole are used. Resin binders include polycarbonate, polyester, polyamide, and polyurethane.

Polymers and copolymers of epoxy, silicone resin, methacrylic acid ester, etc. are used, but compatibility with the charge transport substance is important in addition to mechanical, chemical, and electrical stability, adhesion, etc. In order to maintain a practically effective surface potential, the thickness of the charge transport layer is preferably in the range of 3 to 30 μm, and more preferably in the range of 5 to 20 μm.

Although providing the coating layer 4 is not essential in the present invention, it is desirable to provide the coating layer in order to meet the recent demand for improved durability of photoreceptors.

The coating layer 4 has the function of receiving and retaining the charges of corona discharge in a dark place, and has the ability to transmit the light to which the charge generation layer is sensitive, and transmits the light upon exposure, and the charge generation layer It is necessary to neutralize and eliminate the surface charges by injecting the charges generated when the surface charges reach 1. As the coating material, organic insulating film-forming materials such as polyester and polyamide can be used. In addition, these organic materials, glass resin, Si
It is also possible to use a mixture of inorganic materials such as No. 20 and materials that reduce electrical resistance such as metals and metal oxides. The coating material is not limited to organic insulating film-forming materials, and may also be formed using inorganic materials such as 810□, metals, metal oxides, etc. by methods such as vapor deposition and sputtering. As mentioned above, it is desirable that the coating material be as transparent as possible in the wavelength region where the charge generating substance absorbs maximum light.

The thickness of the coating layer itself depends on the composition of the coating layer, but
It can be set arbitrarily within a range that does not cause adverse effects such as an increase in residual potential when used repeatedly and continuously.

Hereinafter, specific examples will be described.

Example 1 1 part by weight of X-type metal-free phthalocyanine containing 240 μg/g of ionic impurities as a charge generating substance, vinyl chloride copolymer resin (trade name MR-1) as a binder resin.
10: Nippon Zeon ■ (manufactured by Nippon Zeon Department) was mixed with 200 parts by weight of dichloromethane and kneaded for 3 hours using a mixer to prepare a coating solution to prepare a coating solution for the charge generation layer.

The ionic impurities referred to here are C1- and So, which are mixed in during the synthetic skin and crystal control process of metal-free phthalocyanine.
, 2-, No, -, etc., but are not limited to these ionic impurities.

Next, 1 part by weight of 1-phenyl-3-(p-diethylaminostyryl)-5-(para-diethylaminophenyl)-2-pyrazoline (Aspp) was used as a charge transport material, and polycarbonate resin (trade name: Panrye) was used as a binder resin.
A coating liquid for a charge transport layer was prepared by dissolving 1 part by weight of L-1225+Teijin Kasei ■ in 6 parts by weight of dichloromethane. Next, a charge generation layer (1 μm) and a charge transport layer (15 μm) were coated with the prepared coating liquids in this order on a polyester terephthalate film on which aluminum had been vapor-deposited. was created.

Comparative Example 1 500 μg of ionic impurities were added to the charge generating substance of Example 1.
A photoreceptor was produced in the same manner as in Example 1, except that X-type metal-free phthalocyanine containing /g was used.

Example 2 The charge transport material in Example 1 was changed to p-diethylaminobenzaldehyde-diphenylhydrazone (ABPH),
A photoreceptor was produced in the same manner as in Example 1 in other respects.

Comparative Example 2 500 μg of ionic impurities were added to the charge generating substance of Example 2.
A photoreceptor was produced in the same manner as in Example 2, except that X-type metal-free phthalocyanine containing /g was used.

Example 3 1 g of the charge generating substance of Comparative Example 1, methanol (reagent special grade)
25rn1. Pure water 25mj! After performing a dispersion treatment using ultrasonic waves for 1 hour while stirring, the metal-free phthalocyanine was separated and dried. The ionic impurity concentration of this X-type metal-free phthalocyanine was measured and found to be 24 μg/g.

A photoreceptor was produced in the same manner as in Comparative Example I except that the charge generating material in Comparative Example 1 was changed to X-type metal-free phthalocyanine treated as described above.

Example 4 Coating liquids for a charge generation layer and a charge transport layer were prepared in the same manner as in Example 1, and the coating liquids were applied to a polyester terephthalate film containing MM of aluminum in the order of the charge transport layer and the charge generation layer. A positively charging photoreceptor having the configuration shown in FIG. 2 was prepared. However, a coating layer not directly related to this invention was not provided.

Comparative Example 3 Ionic impurities were added to the charge generating substance of Example 4 for 500 μs.
/g into X-type metal-free phthalocyanine containing
A photoreceptor was produced in the same manner as in Example 4 in other respects.

Example 5 The charge transport material in Example 4 was changed to p-diethylaminobenzaldehyde-diphenylhydrazone (ABPH),
A photoreceptor was produced in the same manner as in Example 4 in other respects.

Comparative Example 4 500 μg of ionic impurities were added to the charge generating substance of Example 5.
A photoreceptor was produced in the same manner as in Example 5, except that X-type metal-free phthalocyanine containing /g was used.

The electrophotographic properties of the photoreceptor thus obtained were measured using an electrostatic recording paper tester RSP-428J manufactured by Kawaguchi Electric.

The surface potential VS (volts) of the photoconductor is -6 in the dark for the negatively charged photoconductor, and +6 for the positively charged photoconductor with OkV corona discharge. This is the initial surface potential when the photoreceptor surface is charged by QkV corona discharge for 10 seconds, and the surface potential drop ΔV, (volt) when the photoreceptor surface is then held in the dark for 5 seconds with corona discharge stopped. Measure ΔV d/V
s was defined as DDR5 (dark decay rate after 5 seconds). Furthermore, monochromatic light (780 nm) with an illuminance of 1 μW was applied to the surface of the photoreceptor.
) was irradiated and the time (seconds) required for V to be halved was determined to be the half-attenuation exposure amount El/2 (μJ/Cn).

The measurement results are shown in Table 1.

As seen in Table 1, Example 1 and Comparative Example 1, Example 2 and Comparative Example 2. Example 3 and Comparative Example 1. Example 4 and Comparative Example 3. Comparing Example 5 and Comparative Example 4, it was found that the surface potential and half-attenuation exposure were the same, but the dark decay rate after 5 seconds was better in both examples, indicating that the charge of this invention was better. The superiority of generated substances is clear.

〔Effect of the invention〕

According to this invention, in a laminated photoconductor for printers or copiers, ionic impurities contained in metal-free phthalocyanine, which is a charge generating substance, are reduced to 250 μg/g.
By doing the following, a photoreceptor with high sensitivity, excellent repeatability, and excellent dark decay characteristics can be obtained.

The photoreceptor according to the present invention is of a functionally separated type, making it easy to consider each layer individually from a functional standpoint, and offering a large degree of freedom in material design. For example, a suitable metal-free phthalocyanine can be selected as the charge-generating material depending on the type of exposure light source. For example, if an X-type phthalocyanine compound is used, a photoreceptor that can be used for semiconductor laser blinking can be obtained. I can do it.

[Brief explanation of drawings]

1 and 2 are conceptual sectional views showing different embodiments of the photoreceptor of the present invention.

Claims (1)

[Claims] 1) In an electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer made of an organic material on a conductive substrate, the charge generation substance of the charge generation layer is metal-free phthalocyanine, and the metal-free phthalocyanine is An electrophotographic photoreceptor characterized in that the proportion of ionic impurities contained is 250 μg/g or less.